CiviCRM (www.civicrm.org) is a nice Open Source CRM which is very well integrated in drupal. To create a Survey with CiviCRM you start with creating the questions as custom fields. An obvious choice would be to then create a CiviCRM profile. But a CiviCRM profile...

Pu is an abstraction, comparable to R in math.
It's like a mathematical set of all mental components you classify as "don't know or don't understand". It has no counterpart in the real world, it only exists in your mind.

The contents of the mathematical R are the same for everyone. Sometimes hard to understand...